NAVAL GUN MOUNTINGS These may be divided into two main classes :—(A) Deck Mountings attached to the ship taking guns in classes (I), (2) and (3). (B) Turret Mountings built into the ship to take guns in class (4). These are invariably worked by power, usually hydraulic, though certain nations, among them the United States, prefer electric power, and others a combination of both.
Considerations Affecting the Design of Naval Guns and Mountings.—The gun design is to some extent affected by the mounting conditions particularly as regards the gun's weight and the position of its centre of gravity. If the gun is for a deck mounting and for high angle purposes, it is desirable to keep its axis of suspension as low as possible for reasons connected with the ship's stability and for convenience in hand loading. Conse quently, the centre of gravity must be close to the breech end, and the recoil must be short to avoid fouling the deck at high elevation. Also the gun should be heavy rather than light, or severe stresses may be brought on the mounting and deck struc ture during the short recoil.
If the gun is required for mounting in a turret, its axis of suspension should be as nearly as possible over the roller path on which the turret revolves, to reduce structural stresses incurred by the weight of the gun which in the case of in. guns exceeds 00 tons. The axis should be as close to the front shield as possi ble, so that the opening in the armour necessary for full elevation is as small as possible. Consequently the position of the gun's cen tre of gravity may affect the diameter of the turret on account of the length of gun within it and so may affect the beam of the ship. This may be limited by available docking accommodation. The weight of the gun, mounting, and turret armour appreciably affect the ship's displacement, and should be kept as light as possible. This has led to double and triple gun turrets. The turret as a whole must be balanced, hence the weight of the gun must be compensated by the disposition of the loading machinery in the revolving structure. The heavier the gun the greater is
the weight entailed in such machinery or in the thickness and overhang of the rear shield. The design of the mounting is affected by the class of ship for which the gun is required and by the position in the ship in which it is mounted.
The first consideration in selecting the position for mounting a gun is to obtain as large an arc of fire as possible. The centre line is naturally the most favourable for this purpose, and this has been universally adopted for the primary armament of battle ships since the "Dreadnought" era. The selection of position has a large influence on the arrangement of the ship as in addition to the disposition of magazines and shell rooms, the effects of severe blast on the deck, superstructures and personnel must be met. Freeboard, or height above the waterline, is of importance, and lack of this severely handicapped the British ships in the Coronel action (q.v.).
Important requirements of a naval gun mounting are —(i) Safety under all conditions of use. (2) Protection by armour from enemy action. For the safety of the ship, it is essential to reduce fire and explosion risk to a minimum, particularly as the gun's ammunition is in close proximity to the gun. This is effected by suitable breaks in the train of ammunition supply between the magazine and gun, also by enclosing the ammunition in flash-proof cases in addition to hoists. For heavy guns, air blast is provided, which operates automatically on opening the breech mechanism, and expels gases out of the muzzle of the gun. Water sprays also are fitted to drown any smouldering residue which may be left in the gun chamber or on the breech block. The safety of the gun's crew in operating turret machinery, and of the ship's personnel and ship's structure, is effected by suitable interlocking arrangements and automatic danger signals, which ensure the proper sequence of operations, and prevent the gun from being trained on a bearing where the line of fire is masked by ship's fittings, or where blast effects would be serious.